The present invention relates generally to fasteners and anchors for mounting objects to structural members. More particularly, the present invention relates to expandable fasteners which provide enhanced load bearing capability when utilized in conjunction with drywall, paneling, plaster, or other structural members which, when used, have a rearward cavity.
Traditionally, wall fasteners of several types have been used. One method of mounting an object to a structural member is to place a standard screw or nail directly into the structural member. However, many structural members cannot provide the necessary support for standard screws or nails to bear the weight of a suspended object. This is the case with the interior walls of many residential, commercial and industrial buildings which are fabricated from drywall, paneling, plaster or similar structural members.
The interior walls of many homes are fabricated of drywall or some type of plasterboard. For example, sheets of drywall are fixed to a wooden frame such that a rearward cavity exists behind the drywall within the wall. Thus, when an object is affixed to the wall by means of a standard screw or nail, only a portion of the screw or nail typically remains in contact with the drywall. The remainder of the screw or nail protrudes behind the drywall into the rearward cavity, this protruding portion not providing any support for the suspended object.
Generally, applicant is aware of two types of wall anchors which have been developed to alleviate this problem. The first type of wall anchor is similar to a conventional nail or screw in that it consists of a single element which is driven directly into the wall. Such anchors commonly consist of a long slender shaft with a series of extending flanges or stops. Anchors of this type are shown in U.S. Pat. Nos. 2,751,052 to Flora and 3,983,779 to Dimas.
Such anchors have several disadvantages. Once the anchor is inserted into a wall, the flanges provide some resistance to anchor removal which provides the anchor with additional support. However, because the flanges are fixed and extend radially from the shaft of the anchor, portions of the wall adjacent to the bore created by the anchor are damaged by the flanges. This weakens the wall in the vicinity of the anchor, and makes it more likely that the suspended object will pull the anchor through the wall.
A second type of wall anchor includes a means for expanding the anchor within the rearward cavity once the anchor has been inserted into the wall. This type of device conventionally includes two or more separate elements, one element consisting of an anchor body and the other element providing a means for expansion. This expansion element is often a screw or nail. Devices of this nature are disclosed in U.S. Pat. Nos. 4,322,194 to Einhorn, 4,500,238 to Vassiliou, and 4,221,154 to McSherry.
Since such wall anchors generally provide greater expansion within the rearward cavity, they are generally capable of retaining heavier loads than single piece anchors. However, such anchors are often difficult to install and use. Many of these anchors require a predrilled hole, and the anchor is inserted into the predrilled hole. Predrilling the hole takes additional time and can be quite costly when large quantities of wall anchors are being installed.
One type of drywall fastener which does not require a predrilled hole is shown in U.S. Pat. No. 4,902,179 to Harker. This drywall anchor can be driven into a drywall board or wall by an ordinary hammer and includes a tapered portion which facilitates a clean and gradual cut through the wall. Further, an open portion within the drywall anchor can receive wall debris during penetration of the wall. However, the tapered portion does not facilitate installation of this drywall anchor into the wall by drilling or other rotational means.
Another wall anchor commonly used in buildings consists of spring biased, winged toggles which extend from a threaded nut. This threaded nut is used in conjunction with a conventional screw which is inserted through the object to be supported. While the winged toggles are in their folded position, the threaded nut passes through a predrilled hole in the wall and enters into the rearward cavity behind the wall. Once the winged toggles enter into the rearward cavity, the spring forces the toggles open. Once this has occurred, the screw is tightened until the toggles contact the interior side of the wall. At this point, the object is retained by the screw to the wall. However, it is sometimes desireable to remove and replace the object being supported. To do so, it is necessary to remove the screw from the threaded nut. However, when the screw is removed from the threaded nut, the threaded nut falls away from the predrilled hole into the rearward cavity. Thus, such wall anchors cannot be readily reused.
Wall anchors of this type can also be difficult to install once inserted into the wall. The spring mechanism releases the toggles only after they are completely within the rearward cavity. If any portion of the toggles remain within the predrilled hole, the toggles will not open. Once the toggles do open, there is a distance between the interior surface of the wall and the toggles of at least the length of a single toggle. When the toggles are suspended in the rearward cavity, rotation of the screw often also turns the toggles and, thus, the toggles are not drawn back towards the interior surface of the wall. To secure the anchor in position, the user often must first pull the screw away from the wall, thus pulling the toggles into contact with the interior surface of the wall. While holding the screw and the object to be suspended in this position, the user must then rotate the screw to draw the toggles towards the interior surface of the wall. This can be a difficult as well as time-consuming procedure.
Other multiple element wall anchors exist which do not utilize spring biased toggles. However, these anchors also have disadvantages. These anchors typically rely on the deformation of some portion of the anchor for expansion and retention of the anchor. Such an anchor is shown in U.S. Pat. No. 3,437,084 to Pacharis. This type of anchor is often ineffective because it fails to provide an adequate wall retention spread width for the weight of the object to be suspended. The wall retention spread width is the radially extending distance from the center of the expansion element to the furthest point of contact between the anchor and the interior surface of the wall. Since with these types of anchors, the deformable legs deform at a location intermediate the ends of the deformable legs and provide the sole means of engaging with the interior surface of the wall, the wall retention spread width provided can be no greater than one-half of the total length of the deformable legs. In many cases, the wall retention spread width is only one-third to one-fourth of the length of the deformable legs which extend into the rearward cavity. Thus, with these types of anchors, it is necessary to have deformable legs which are at least two, and often three to four times as long as the wall retention spread width desired. This requires additional material and limits the effectiveness of such anchors when utilized in a rearward cavity of limited depth.
Furthermore, since it is most desirable for the deformable legs to make contact with the interior surface of the wall in a predetermined triangular configuration, such anchors are typically most effective when utilized with a wall of the thickness for which that particular anchor was designed. Thus, multiple sized anchors are needed to accommodate various wall thicknesses, and further, the user needs to determine the thickness of a wall prior to installation.
A further limitation of many existing anchors is that they do not permit the installer to know when the anchor is securely in place. When a screw and a nut are used to clamp an object, one knows the nut is secured once turning of the screw becomes difficult. However, many of the existing anchors do not provide such notice to the installer. Therefore, the retention portion of the anchor could be pulled partially, or entirely, through the wall. This not only damages the wall, but also renders the anchor unable to provide support.
Accordingly, an object of the present invention is to provide a wall anchor which can be installed through a predrilled hole, or alternatively, by hammering or drilling the anchor into a wall.
A further object of the present invention is to provide a wall anchor which permits multiple removal and reinsertion of the actuating element, and which remains in position for reuse after the actuating element is removed.
Still another object of the present invention is to provide a wall anchor which minimizes the damage caused to the wall adjacent to the installed anchor.
Yet another object of the present invention is to provide a wall anchor which enhances load bearing capacity by increasing the wall retention spread width while at the same time minimizing the overall length of the anchor.
A still further object of the present invention is to provide a wall anchor which can be used on walls of varying thicknesses.
Still another object of the present invention is to provide a wall anchor which requires a reduced threading torque to be applied to the actuating element in order to attain full expansion of the retention element.
Yet another object of the present invention is to provide a wall anchor which does not require the user to pull the retention element against the inside surface of the wall before tightening the actuating element.
These and other objects of the present invention are attained by the provision of an expansion-type anchor having a generally hollow body, a nut element, at least one, and preferably two, retention elements and an actuating element. The retention elements are pivotably connected to the nut element and transition from an orientation substantially parallel to the body to an extended position substantially perpendicular to the body once positioned behind the wall in the rearward cavity. At the end of the body opposite the nut element, the body includes an anchor head which is of greater dimension than the remainder of the hollow body. The anchor head is positioned generally transverse to the longitudinal axis of the body and secures the body to the exterior surface of the wall. The actuating element is positioned in an opening in the anchor head and extends within the length of the body to engage the nut element. Flanges extending from the anchor head preclude rotation of the anchor once the anchor head is embedded in the exterior surface of the wall. In some preferred embodiments, rotation of the actuating element creates a force which is exerted on deformable legs to cause the retention elements to transition from an orientation substantially parallel to the body to an extended position substantially perpendicular to the body. Continued rotation of the actuating element draws the retention elements into contact with the interior surface of the wall. Once the body is in place, the actuating element can be removed to install the object to be suspended and the anchor body will remain in place.
Some preferred embodiments of the present invention include a penetration element with an interior cavity. This penetration element is affixed to the portion of the actuating element which extends through the nut element. Due to the fluted nature of the penetration element, the anchor may be inserted through a predrilled hole or, alternatively, hammered or drilled into the wall. Once the penetration element has completely pierced the wall and entered into the rearward cavity, the anchor is readily secured into position. Also, some preferred embodiments include retention elements which are spring biased. Thus, when the retention elements are completely within the rearward cavity, a spring forces the retention elements into their extended position.
Other objects, advantages and novel features of the present invention will become apparent from the following detailed description of the invention when considered in conjunction with the accompanying drawings.